linearity vs linear

linearity is a noun but linear is not a noun.

Word	Noun	Adjective	Verb	Adverb
linearity	Yes	No	No	No
linear	No	Yes	No	No

linearity (noun)	linear (noun)
the property of having one dimension

linearity (adjective)	linear (adjective)
	of or in or along or relating to a line; involving or having a single dimension
	designating or involving an equation whose terms are of the first degree
	of a circuit or device having an output that is proportional to the input
	measured lengthwise
	(of a leaf shape) long and narrow